Skull and Bo7ies of the Trmih of Comuioji Fowl. 25 



For the Tarsus and Carpus and Scapular Arch^ see Professor 

 Geg-enbaur^s Monographs,, Untersuchung-en zur Verg-leichenden 

 Anatomie der Wirbel thiere^ 1864^ 1865, Hft. i. pp. 38, 40^ 

 51, 93; Hft. ii. p. 27, et passim. 



For the Homologies of the digits of the fore-limb see Gegenbaur, 

 1. e, Hft. i. p. 41. 



6. Skull and Bones of the Trunk of Common 

 Fowl {Gallus Gallinaceus). 



The skull of the Common Fowl differs from that of the Common 

 Pigeon in being less pneumatic and polished ; and in being less 

 evenly globose in its fronto parietal and fronto nasal regions ; in 

 the shape of its nostrils ; in the much smaller obliquity of its quad- 

 ratojugal arch ; in its much smaller occipital angle^ superethmoidal 

 and interorbital vacuities ; in its possession of a rudimentary vomer, 

 of a larger external angular process to the lower jaw ; in the abor- 

 tion of the posterior crus of its os quadratum or incus, the anterior 

 head retaining two facets, one for the prootic and the other for the 

 squamosal; in its differently-shaped palatines, pterygoids, squa- 

 mosals, and lacrymals, and in the absence of an azygos supra occi- 

 pital fontanelle, or venous canal. The basioccipital articular con- 

 dyles, however, of the Fowl and Pigeon, resemble each other in 

 being emarginated in the middle line superiorly, as though to 

 indicate, as the single occipital condyle does more plainly in the 

 Reptiles, its primitive composition out of three elements. The cup 

 of the atlas is alike in both families, imperfect and not typically 

 avian, and the two families resemble each other yet further in the 

 absence in both alike of the lateral vertebral canal in the axis and 

 atlas. 



There are in the Common Fowl seven- vertebrae which carry 

 nnanchylosed ribs. One of these vertebrae, however, is itself an- 

 chylosed to the sacrum, and is sometimes reckoned as a sacral 

 vertebra ; but it may be better, perhaps, reckoned in the dorsal 

 series, as its ril) is, besides being unanchylosed and articulated just 

 as the ril)s placed anteriorly to it, in such relation in the fresh state 

 with the lower end of the lung as to form an indentation upon it. 



